The building and construction industry uses fabrics, polymer films, and other such web-like materials extensively to cushion, insulate, seal, and/or protect various components of a building as it is being constructed. Examples of these web-like materials include housewrap, lumber wrap, roof underlayment, flashing, etc. These materials should be tough and strong to withstand the rigors of the building process. These materials often need to be water repellant, to protect the interior of the building from moisture damage; however, it is also desirable that the materials are breathable in order to allow water vapor generated in the building (e.g. steam, expiration, evaporating water) to escape rather than retained inside the building and causing moisture damage and other associated problems. These building materials may also play a role in insulating the building. Finally, of course, it is desirable to have the materials available at a reasonable cost.
For instance, housewrap materials are used to protect a building from water and wind damage during construction, especially in cold climates. Housewrap materials are typically attached or secured to the outer surface of framing or sheathing in the walls of buildings. Housewrap materials must be permeable to water vapor to allow water vapor to escape from the wall to which the film is secured to prevent water damage or the like. On the other hand, the housewrap materials should be sufficiently impermeable to air and liquids to insulate the wall against wind and rain or other precipitation. Further, housewrap materials should have adequate tensile and physical properties such as break strength, elongation, tear strength, shrinkage and puncture strength to avoid damage during installation and to facilitate durability.
To provide housewrap materials and other breathable materials suitable for construction and similar heavy duty use with sufficient strength and toughness, it is often desirable to use strong and/or tough nonwoven and/or woven fabrics.
The Sheth U.S. Pat. No. 4,929,303 discloses composite breathable housewrap materials which comprise a breathable film formed of linear low density polyethylene and a nonwoven fabric formed of cross-laminated fibers. The breathable film is formed by cast extruding a precursor film onto a roller, stretching the precursor film to impart permeability, heating the nonwoven fabric, and pressing the heated fabric to the film to bond the fabric and the breathable film. Owing to these successive processing steps, the manufacture of the disclosed housewrap materials can be somewhat cumbersome and expensive.
Patent Application Publication US 2004/0016502 A1 discloses breathable materials which comprise a low-elongation fabric layer coated with a microporous coating comprising a crystalline polymer composition and a filler. This application also discloses methods for extrusion coating the low-elongation fabric with the microporous-formable polymer coating, then incrementally stretching the coated fabric in order to render the polymer coating microporous. This invention has the advantage of being manufactured in a single-pass process. However, the invention requires the capital expense of machinery for an incremental stretching station or stations, and the ongoing operating expenses associated with running such incremental stretching equipment.
Accordingly, a need exists for improved breathable materials, including those which may employ relatively strong or tough woven or nonwoven fabrics, and for methods for facilitating the manufacture of such materials.